Call loss probability and block rate

Quan: blocking rate is related only to the desired but non available trunks(system is 100% bussy).That means if you havea max. number of 1000(available) lines of a PBX systems (traffic capacity of equipment)and the blocking rate you signed for is 2% you will be able to deal in therms of your contract only with 1020 simultaneous calls(desired) and still being inside your contract therms. That means you will never ever(not even in the bussy hour) have more than 1020 simultaneous calls.So if your BHCA is bigger than 1020 you are not inside the contract and there’s nothing more you can do but to change your PBX capacity.Why? Because you can not change subscriber’s profile!At least that’s how in GSM is

Quan: blocking rate is related only to the desired , but unavailable, channels(system is 100% busy).That means if you have a max. number of 1000( available) lines of a PBX systems (traffic capacity of equipment)and the blocking rate you signed for is 2% you will be able to deal in terms of your contract only with 1020 simultaneous calls(desired) and still being inside your contract terms. That means you will never ever (not even in the busy hour) have more than 1020 simultaneous calls otherwise your planning was wrong and you are not inside the contract and there’s nothing more you can do but to change your PBX capacity. Why? Because you can not change subscriber’s profile! At least that’s how in GSM is.

I work in GSM and GSM is a system without queuing i.e. any call attempt that was not handled in its serving cell or adjacent cells using direct retry will be lost (that means we use erlang B formula) and not erlang C formula( that is for queuing systems i.e. any call that is not handled will be in queue for some seconds than re-handled) so call loss probability is somehow different for those different systems.

At least that’s my opinion